/**
 *  该文件的适用于创建一个为 Count组件服务的Reducer，Reducer的本质就是一个函数
 */
import {INCREMENT, DECREMENT} from "./constant";

const initState = 0;        // 初始化状态
export default function counterReducer(preState = initState, action) {
    const {type, data} = action;
    switch (type) {
        case INCREMENT:
            return preState + data;
        case DECREMENT:
            return preState - data;
        default:
            return preState;
    }
}
